The present invention relates to an electrical drive device for a vehicle window regulator. More precisely, the invention relates to an electrical control of a cable-actuated window regulator which comprises a brake for preventing the reverse movement of the regulator when a force is exerted on the window pane in order to open it.
The irreversibility of the drive device is necessary in order to prevent acts of vandalism not involving breakage of glass or forcing of the locks. In manual drive devices, there is provided between the shaft of the crank and the cable drive drum, an irreversibility device commonly called xe2x80x9cbrake boxxe2x80x9d, which comprises a helical spring housed in a fixed cylindrical sleeve and whose ends are curved axially inwardly. The drive drum comprises two diametrically opposite axial fingers and the shaft of the crank is also equipped with two diametrically opposite axial fingers interposed with clearance between the fingers of the drum. When a finger of the crank abuts on one spring end, the spring contracts and may rotate freely in the sleeve, this rotating the drum and maneuvering the windowpane.
Inversely, when a force is exerted on the windowpane to open it, for example, a finger of the drive drum abuts on one spring end in the sense of radial expansion thereof. The spring then abuts on the inner wall of the sleeve, and the friction of the spring against the wall brings about a braking of the spring. The forces of friction are calculated so that the spring expanded in the sleeve is immobilized by friction, which prevents the reverse rotation of the crank.
In window regulators actuated by an electric motor, the motor generally drives an endless screw which cooperates with a helicoidally toothing of a wheel. The screw pitch, the shape of the threading and the shape of the toothing are calculated so that, if the drum is urged in rotation by exerting a force on the windowpane, the endless screw is not driven in rotation. The output of the kinematics is low and less than 0.5, in order to ensure irreversibility of the device. The driving torque is therefore high, which brings about high energy consumption.
U.S. Pat. No. 5,207,393 proposed equipping an electrical drive device for the window regulator, with a brake box functionally identical to the brake box of a manual drive device. In this device, the worm wheel driven by the endless screw is disposed between the cable drive drum and the brake box. The fingers of the drum pass through openings made in the wheel and the wheel comprises two opposite sets of axial fingers. One of these sets is disposed in the brake box and the other set is arranged in housings made in the drum and is intended to drive the drum in rotation under the action of the motor. As the wheel is disposed between the drum and the brake box, the dimension of the device proposed by U.S. Pat. No. 5,207,393, in the direction of the axis of rotation, is greater than the dimension of a manual drive device which comprises only a drive drum and a brake box axially connected to the drum. On the other hand, the pieces used, particularly the drive drum and the box, cannot be used equally well for a manual drive device and for an electrical drive device, due to the increase of the axial dimension of the fingers of the drum in the electrical drive device.
On the basis of the state of the art disclosed by U.S. Pat. No. 5,207,393, the first object of the present invention is to propose an electrical drive device for a cable-actuated window regulator equipped with a conventional brake box which presents dimensions which are transversely with respect to the door equipped with the device, and at the most equal to those of a manual drive device.
It is another object of the invention to propose an electrical drive device for window regulator which comprises pieces identical to those of a manual drive device, in order to reduce costs of the tools and the number of pieces in stock.
An electrical drive device for a cable-actuated window regulator includes a casing, an electric motor mounted on the casing, a cable winding drum mounted to rotate about an axis x in the casing and presenting on one of its faces at least a first axial finger, and a gear wheel mounted to rotate about axis x on the casing and capable of being driven in rotation by the motor, the wheel including at least a second axial finger.
A helical spring of axis x is disposed in a brake box of axis x formed in the casing and includes inwardly curved ends. The first finger and the second finger are disposed in the brake box, are equidistant from axis x, and extend circumferentially with clearance inside the turns of the spring.
The ends of the spring and the fingers are disposed so that, when the motor drives the wheel, the second finger abuts on a spring end to compress it axially so that it can rotate at the same time as the gear wheel. When the drum is urged in rotation, the first finger abuts on a spring end and provokes an axial extension of the spring, preventing the rotation of the wheel further to contact of the spring with the brake box.
The casing includes a cylindrical housing of axis x for receiving the drum and a cylindrical sleeve of axis x open at its end opposite the housing and constituting the brake box. The wheel includes a toothed ring surrounding the sleeve and having a frontal wall obturating the opening of the sleeve. The second finger extends axially from the frontal wall inside the ring.
The axial dimension of the device proposed is thus equal to the dimension of a manual drive device in which the shaft of the crank passes through an opening made in the bottom of the brake box. The drum is identical to that of a manual drive device. The casing of the device proposed is virtually identical to that of the casing of the manual drive device, as, instead of making a hole in the bottom of the brake box for the passage of the shaft of the crank, this bottom is removed to make the opening of the sleeve.
The casing is advantageously produced by stamping a first plate in order to make the housing of the drum and by stamping and cutting out a second plate in order to produce the cylindrical sleeve, the two stamped plates being joined along a plane of join located in the orifice of the drum housing. The inner diameter of the sleeve is preferably greater than the diameter of the drum housing.
According to another advantageous characteristic, the electric motor comprises a drive unit and a hood and the wheel is mounted on the hood. This hood is fixed on the casing.